The Will of the Empress by Tamora Pierce

This is the first (and only?) book in The Circle Reforged series, the follow-up to The Circle Opens quartert. (You can read about the two previous quartets in this series here and here.) In this book the four teenagers who were the center of the previous series are once again brought together. Most of the story takes place four years after the the other books, although there is some introduction before then. The basic beginning is that while her three friends have been traveling all over the world for the past two or three years, Sandry has remained at home helping her uncle run his land. His friends begin returning, but a distance has grown between them all, from their time apart. The distance is emotional as well as magical. The four teens once had strong connections between their magic, but that is no longer the case.
Sandry has been called to visit her cousin, the Empress of Namorn, and her uncle sends her three friends along as protection, despite the separation they feel from each other. While in the Empress's court, Sandry realizes that her cousin has been causing hardship on her lands, and wants Sandry to marry so she will gain control over them. While Sandry is contending with these political machinations, the other three are fending off various bids for their attention. They are all powerful mages, and the Empress wants them in her service. For Briar that means offering him access to her greenhouses; but for Daja and Tris, the Empress does not know what to offer. When the bids for power become dangerous, Sandry and her friends realize that they must leave. But first Sandry must figure out what to do in order to protect her ancestral land from further disruption by the Empress.
I enjoyed this book more than the others in this series I think. The others were fun, but had no real depth, and were a little bit formulaic. This one was a little bit more complicated, and now that the main characters are older, the issues that they must confront are more interesting. They must learn how to trust each other again, and also how to trust themselves. This book could be read without reading the others, but the reader might be a little confused by some of the references to previous characters and happenings.